NavList:

 Paul Hirose
You spoke of aircraft compass swinging.  In the RAF it was usually a shared job between the Instruments Fitter and the Aircrew.  In the Vulcan it was shared between the Co-Pilot (to keep the auxiliary power pack refuelled), the two Navigators, and the Tug Driver.  On your first day at Nav-School you were issued to a desk on which was set out your nav-bag, a nav-rule, a Dalton computer, and a pencil box  containing: a Douglas protractor, a pair of dividers, an eraser, a couple of pencils, a sharpener, a red/blue crayon (for making danger areas, and updating lines of magnetic variation), and a key-compass corrector Mk1 (see photograph).
My first experience of compass swinging was as one of the more senior cadet pilots on London University Air Squadron when I was required to taxi out in a Chipmunk T10 with the compass book on my knees to meet an instruments chap with a landing compass at the compass swinging area.  It was pouring down, and he was dressed in oilskins down to his toes, so I decided that being Aircrew was certainly the best job.  Then I proceed to taxy onto the desired headings while he tailed behind with the landing compass.  I had to wait on each heading until he appeared off my port wing tip (putting him automatically into his next position, and he raised or lowered his arm a few times to indicate the exact landing compass heading.  After the check-swing, there was a brief wetting while he shouted into the cockpit to tell me what to make the P-type compass read by sticking his compass corrector key (I didn’t have one in those days) into the correct hole and twisting it.  The correct hole was located using what I was later to learn as the ribald mnemonic (‘British fore and aft-Chinese athwartships’). 

At Nav-School gyro compass swinging and Fourier analysis was a major part of the course and the exams.  Compass swinging the twin Smiths MFS and the two pilot’s E2s in the Vulcan was a great way of being away from the Squadron for a morning (and most of the afternoon if you could manage it), especially on a sunny summer’s morning with the skylarks singing.  The Nav-Plotter sat in his seat, directed operations, and filled in the two compass logs, the Nav-Radar (me), always the dogsbody in a Vulcan crew, trailed round with the Watt’s Datum Compass lining it up on two rods dangling from the port wing; climbing back on board occasionally and at the end to double check the Nav-Plotter’s arithmetic.  The Co-pilot sat in his seat ensuring the Rover AUPP didn’t run out of fuel and doing what he was told re correcting the pilots E2s.  The Tug driver had done this 100s of times and knew where to stop off by heart.  One was left wondering what the point was of swinging to 0.1 of a degree while being towed by a massive steel tractor using a 30ft long heavy steel tube towing arm, but 'ours not to reason why'.  We got rather good at this and became one of the ‘go-to’ crews to swing problem aircraft, which as I’ve said, was a great way of getting away from the office.   In wet cold weather we cheated.  The aircraft had been retro fitted with a very accurate gyro, surplus from somewhere or other.  We’d check the initial heading with the Watt’s Datum Compass and set the gyro to it.  We’d then complete the swing using the gyro which read to 0.1 degree, checking with the watt’s datum occasionally to check the gyro hadn’t wandered off.  This was rather frowned upon, but it seemed to work very well and was much faster than the Watt's Datum Method. 

I only did one air swing myself.  It was in a Domine T1 while completing my Aerosystems Course.  We did it using celestial with the Smiths Mk2 peri-sextant. The mounting had been modified to include a vernier scale glued to the heading/azimuth ring.  In theory, this is the most accurate way to swing a compass, because you are in air with all the aircrafts engines and systems operating.  The problem is converting celestial’s ‘true’ to ‘magnetic’ for the compass system, because variation varies not just with location and date but also throughout the day.  Fortunately, we still had an Admiralty Compass Observatory in the UK in the 1970s who, if you supplied a Decca position, time, and altitude, were able to give you a very good estimation of variation.  I did read, much later, that 100Sqn air swung their Victor B2s in the 1960s for navigation competitions, but they didn’t publicise it at the time, because it was, of course, ‘gamesmanship’.

I did the occasional ground swing the Dominie T1 while I was teaching Compasses at Nav-School.  I never bothered with the Piper L4H I was part owner of, but I did swing the little Mosler Pup I owned, mainly for fun, pushing the aircraft round the Compass Pan at Cranwell and using a hand bearing compass.  I dare not do it with the engine running in case the aircraft decided to fly away by itself.

I only flew in a B52 H Model a couple of times as an umpire in the 1970s (Captain Boserdet & Captain Ham).  As you said, it was a long climb from downstairs to upstairs.  The crew’s choice of rations was peanut butter and Jello sandwiches.  The two chaps upstairs facing backwards checked in on the RT as ‘Offense’ and ‘Defence’.  As I Recall, my safety briefing should the crew start ejecting in an emergency was to wait until the one of the Navigators had ejected downwards through the floor and jump through the hole he left. DaveP

A few videos:
https://www.youtube.com/watch?v=XluTOwL90h8 N1 Compass

https://www.youtube.com/watch?v=SpAgQxUxdwc Introduction of Domie T1

https://www.youtube.com/watch?v=5gMmu6FMrZs RAF Navigator Training 1967-68

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